Approaching a new theory on Caspian Sea response to global climate changes during MIS2 - MIS1: generalization and reassessment of δ18O data

Abstract

The study represents correlation δ¹⁸O records from the Caspian basin together with available stable oxygen data on the continual sequence of deep-sea cores and on Kara-Bogaz-Gol Gulf, nearby lakes, and caves to complete palaeogeographical reconstruction of the Caspian Sea region. Typical Quaternary caspian ostracods shells and valves were measured for the δ¹⁸O analysis. Oxygen isotope data allowed to correlate region transgressive-regressive events with glacial-interglacial rhythm and global climate changes. It was distinguished three main evolution stages of the Caspian Sea region, including the Last Ice Sheet degradation with a series of step-like environmental shifts matching the sequence of abrupt cooling/warming events; abrupt warming at the beginning of the Holocene; and climatic fluctuations of a smaller scale and different sets during the second part of the Holocene. It was established that Caspian Sea level oscillations occur as a response to climatic changes among numerous probable causes. Transgressions were usually accompanied by the freshening of water and cold climate while regressions were primarily correspond to increased salinities and warm climate. The reconstruction of the Caspian Sea hydro-climatic changes was confirmed by observed similar trends in the oxygen isotope record of nearby regions.